boot - Migrating Windows 7 from MBR to EFI without formatting

28
2014-03
  • djechelon

    Based on the experience documented in Migrate from MBR to UEFI with an encrypted system partition

    I'm considering the opportunity to migrate Windows 7 from the plain ol' MBR to the new GPT/UEFI boot before upgrading to Windows 8. I'm linking my previous post because when migrating Linux I experienced a few issued and learnt a lesson about GPT: don't trust simplicity. I'm not working on the same computer as the other post!!

    Anyway, to make it short, I know that in order to boot from UEFI I need an EFI boot partition on first instance, then I must make sure that Windows restores the boot structures correctly once they are missing. I don't have encrypted partitions or other fancy things on this computer, just to clarify.

    I'm asking you for any direct experience in the conversion.

    Flight plan:

    • Backup important data
    • Run the tool to convert MBR to GPT from the system
    • Shut down and physically disconnect unneeded hard disks (just in case..)
    • Reboot into DVD recovery mode
    • Let recovery fix the boot problem (perhaps auto creating the EFI boot partition)
    • If it doesn't work on auto repair mode use bootrec /rebuildBcd
    • If that doesn't work I'm screwed

    Questions:

    1. Does this tutorial on MBR/GPT conversion work on a live Windows system? The last time I used it it ran on a non-system disk and I could successfully shut down the machine the clean way
    2. Does Windows recovery automatically create the EFI boot partition shrinking the system partition?
    3. In case I'm screwed (read above) can I create the EFI Boot partition with GParted or similar tool? How large should it be? Then, does Windows Restore do its job?
    • Answers
  • Rod Smith

    Such a conversion is possible, but is also risky and a bit of a pain. Something like your outline might work, but it's been at least a year since I did anything along those lines, and I don't recall the details of what I did. This article describes the process; however, it's based on using DUET to create an EFI environment on a computer without EFI support in the firmware. Thus, you'll need to ignore all the references to DUET if you follow that procedure. (This actually simplifies the conversion.)


    • Related Question

    Problems with Windows 7 + Windows Server 2008 R2 multibbot on EFI computer
  • Al Kepp

    We have a new computer, and I am a bit confused from its new features I don't know from older hardware. It is a high end PC based on socket 2011. I want to use an SSD disk for operating system, and I want to install there a multiboot with Windows 7 x64 and Windows Server 2008 R2. So I put this new SSD disk into this new computer, put Windows 7 DVD into drive, and installed. I split the drive into 2 partitions during installation of W7 to let me install WinServer later. W7 works perfectly, no problems.

    But now I insterted Windows Server installation DVD, and I want to install it to the second partition. But the installation DVD doesn't want to install the system and complains that Windows Server 2008 R2 cannot be installed on disk drives with MBR on EFI computers. It shows correctly the SSD disk with its three partitions (one hidden small 100 MB as used in all W7 installations, then W7 partitons, and one empty partition where I want to put my new Windows Server installation), but it simply refuses to install itself in there. How to solve this problem?

    I have a working W7 installed on that disk, is it possible to move it to GPT without losing that partition? And if that's not possible, how can I install W7 to an empty SSD disk and force it to GPT on installation? I am affraid it get a MBR automatically without user intervention. Or should I put this SSD disk to anotehr W7 computer and use its standard Windows disk drive manager to put there a GPT?


    • Related Answers
  • tapped-out

    There is no way to convert an existing MBR disk to GPT. If you want to install Windows 7 first and have the disk as GPT, you need to do the following from Windows Setup before you partition disks:

    1. press Shift+F10 to access a command line
    2. type diskpart to access Windows' command-line partitioner
    3. type list disk and take note of which disk you want to convert to GPT
    4. type select disk n, where n is the disk from step 3
    5. type clean to delete all partitions on the disk
    6. type convert gpt to convert the disk to GPT

    At this point, you should be able to close out of the command prompt and proceed normally with Setup.

  • zozo

    I suppose your problem is solved now but this could help anyway :

    I tried to install srv08R2 with a dual boot with an existing 7 OS installed (2 partitions, one with 7 installed and one "unallocated space").

    But 2 main errors : problem with GPT (srv08 refuses to be installed on a GPT disk) and then another i'll tell about later.

    First : try to boot on an external DVD connected via USB (the device you boot on is the one who tells the installation program if your disk is GPT or MBR... strange i know but i only could admitt it!!!) According to me i booted from an external DVD via USB3. This solves the first problem but another one could occure if ure in AHCI mode :

    Right before installation starts, you could get a message asking you for a missing CD/DVD driver. It's actually the AHCI driver he's asking for. So go the BIOS => USB parameters => set XHCI to auto Then restart on the DVD and you should be able to install your second OS on your partition (no GPT error, no CD/DVD driver missing…). Windows should install on the partition he use to refuse...

    Hope it'll help. Regards.